Typically a large number of reduced volume reactions are carried out simultaneously in one apparatus, with a plurality of reaction vessels being received in a reaction apparatus at one time. Often the reaction vessels are in the form of a tray, known as a microtiter plate, made up of an array of vessels. In one standard microtiter plate, 96 vessels are formed in one array. In order to control and monitor the reactions, the apparatus includes means to monitor the temperature and to control the heating power applied to the reaction vessel contents.
Often, in reactions involving multiple thermal cycles, the cooling part of the cycle is effected using a cooling block and/or a fan blowing cooled air over the vessel or vessels. Often the cooling is continuously present and the heating part of the cycle is carried out against a background of the cooling. Thus, for example, in conventional block thermal cyclers, heating is effected using a direct heater, for example thermal mats, and cooling by either forced air or actively by thermo electric heat pumps. In other thermal cycling apparatus, heating and cooling are effected by shuttling between blown hot air and blown cold air.
There are situations, for example, when it is required to identify what may be a dangerous pathogen, in which it is highly desirable to minimize the time taken by such a reaction. Apparatus for minimizing the time required in the heating part of the cycle is described in UK Patent Nos. GB 2404883B, published on Feb. 27, 2006, and GB 2424380B, published on Jun. 27, 2007, both of which are incorporated herein by reference thereto. In this apparatus, an electrically conductive polymer is employed as, or as part of, the material of the reaction vessel. Cooling is effected using forced cooled or ambient air.
Normally, the maximum cooling rate achievable using forced air is 8° C. per second. A higher cooling rate than this would be very useful. The present invention provides means whereby cooling in biological or chemical reactions requiring thermal cycling is significantly accelerated.